Ethernet has become the de-facto data networking technology. It has been tested over time and has gained dominance in data communications. Currently, Ethernet is being extended to industrial networks where robots, machines, and sensors communicate among themselves to take action collectively. To be suitable for industrial networks, Ethernet needs to overcome some of its weaknesses. One weakness of conventional Ethernet protocol is head-of-line blocking. Head-of-line blocking occurs when Ethernet frames associated with different traffic flows share an egress queue. In one example, a large frame of non-real-time traffic, such as a file download, can delay transmission of frames of time-critical traffic located behind the large frame in the output queue. Delaying transmission of time critical traffic, such as voice or video traffic, can result in poor quality of service for end users.
To avoid some of the difficulties associated with conventional Ethernet, time sensitive networking or TSN standards have been defined. Time sensitive networking is a set of standards developed by the Institute of Electrical and Electronics Engineers (IEEE). Specifically, time sensitive networking standards are being developed by the time sensitive networking task group of the IEEE 802.1 working group. The TSN task group was formed in November of 2012 by renaming the existing audio/video bridging task group. As part of the TSN standard, Ethernet frames can be preempted and fragmented. For example, a low priority frame of non-real-time traffic that may block or delay transmissions of higher priority real-time traffic can be preempted by the real time traffic and transmitted in fragments to the destination. By “preempted”, it is meant that even after the low-priority frame has started its transmission onto the wire to the next hop, the transmission is stopped after some, but not all, of the frame has been transmitted. The higher priority real-time frames are then transmitted. The portion of the frame that has already been transmitted forms the initial fragment, and the remainder of the frame forms continuation fragments
Frame preemption represents a significant shift from conventional Ethernet where a packet is transmitted in its entirety to the next hop once transmission is started and travels as a whole, rather than in fragments. When frames are preempted and fragmented, the impact of preemption and fragmentation needs to be measured. It is desirable that a network test tool be capable of measuring different aspects associated with delivery of preempted frames by the network.
Accordingly, there exists a need for methods, systems, and computer readable media for measuring delivery latency in a frame-preemption-capable network.